1. Field of the Invention
This invention relates to computer networks and communication management, and to the establishment of communication between various users and/or software applications.
2. Background Discussion
The term “The Information Superhighway” is commonly thought of as an extension of the Internet, a network linking hundreds of thousands of computer systems together and communicating via a standard protocol. A computer network is simply a collection of autonomous computers connected together to permit sharing of hardware and software resources, and to increase overall reliability. The qualifying term “local area” is usually applied to computer networks in which the computers are located in a single building or in nearby buildings, such as on a college campus or at a single corporate site. When the computers are further apart the term “wide area network” may be used.
As computer networks have developed, various approaches have been used in the choice of communication medium, network topology, message format, protocols for channel access, and so forth. Some of these approaches have emerged as de facto standards, but there is still no single standard for network communication. The Internet is a continually evolving collection of networks, including Arpanet, NSFnet, regional networks such as NYsernet, local networks at a number of university and research institutions, a number of military networks, and increasing, various commercial networks. The protocols generally referred to as TCP/IP were originally developed for use through Arpanet and have subsequently become widely used in the industry. The protocols provide a set of services that permit users to communicate with each other across the entire Internet.
A model for network architectures has been proposed and widely accepted. It is known as the International Standards Organization (ISO) Open Systems Interconnection (OSI) reference model. (See FIG. 10.) The OSI reference model is not itself a network architecture. Rather it specifies a hierarchy of protocol layers and defines the function of each layer in the network. Each layer in one computer of the network carries on a conversation with the corresponding layer in another computer with which communication is taking place, in accordance with a protocol defining the rules of this communication. In reality, information is transferred down from layer to layer in one computer, then through the channel medium and back up the successive layers of the other computer. However, for purposes of design of the various layers and understanding their functions, it is easier to consider each of the layers as communicating with its counterpart at the same level, in a “horizontal” direction. (See, e.g. The TCP/IP Companion, by Martin R. Arick, Boston: QED Publishing Group 1993, and U.S. Pat. No. 5,159,592. These, and all patents and publications referenced herein, are hereby incorporated by reference.)
As shown in FIG. 10, the lowest layer defined by the OSI model is called the “physical layer,” and is concerned with transmitting raw data bits over the communication channel. Design of the physical layer involves issues of electrical, mechanical or optical engineering, depending on the medium used for the communication channel. The second layer, next above the physical layer, is called the “data link” layer. The main task of the data link layer is to transform the physical layer, which interfaces directly with the channel medium, into a communication link that appears error-free to the next layer above, known as the network layer. The data link layer performs such functions as structuring data into packets or frames, and attaching control information to the packets or frames, such as checksums for error detection, and packet numbers.
The Internet Protocol (IP) is implemented in the third layer of the OSI reference model, the “network layer,” and provides a basic service to TCP: delivering datagrams to their destinations. TCP simply hands IP a datagram with an intended destination; IP is unaware of any relationship between successive datagrams, and merely handles routing of each datagram to its destination. If the destination is a station connected to a different LAN, the IP makes use of routers to forward the message.
The basic function of the Transmission Control Protocol (TCP) is to make sure that commands and messages from an application protocol, such as computer mail, are sent to their desired destinations. TCP keeps track of what is sent, and retransmits anything that does not get to its destination correctly. If any message is too long to be sent as one “datagram,” TCP will split it into multiple datagrams and makes sure that they all arrive correctly and are reassembled for the application program at the receiving end. Since these functions are needed for many applications, they are collected into a separate protocol (TCP) rather than being part of each application. TCP is implemented in the “transport layer,” namely the fourth layer of the OSI reference model.
Except as otherwise is evident from the context, the various functions of the present invention reside above the transport layer of the OSI model. The present invention may be used in conjunction with TCP/IP at the transport and network layers, as well as with any other protocol that may be selected.
As shown in FIG. 10, the OSI model provides for three layers above the transport layer, namely a “session layer,” a “presentation layer,” and an “application layer,” but in the Internet these theoretical “layers” are undifferentiated and generally are all handled by application software. The present invention provides for session control and for communicating with applications programs. Thus the present invention may be described in accordance with the OSI theoretical model as operating at the session layer and application layers.
“Connectivity” and “convergence” have been used to describe two aspects of the communications and computing revolution taking place. In 1994, technology provides to communicate by telephone, pager, fax, email, cellular phone, and broadcast audio and video. However, to use these communication services, you have to employ a telephone number, beeper number, pager number, fax number, cellular number, and each of many email IDs, radio stations and television channels. The user is confronted with an overabundance of methods providing such physical connectivity, one which will only grow in the future.
The types of physical connections are provided by various systems including the Regional Bell Operating Companies, the Long Distance Carriers, the Cellular Networks, and others providing signal-based or wireless communications. The Cable Television Industry provides connectivity for video signals and increasingly other services.